Longitudinal urine drug testing among patients receiving opioids for cancer pain.

Context: To assess for non-prescribed substance use and adherence to controlled medication treatment, urine drug tests (UDT) are recommended for patients receiving opioids for cancer-related pain management. However, the optimal frequency of UDTs during opioid treatment is unclear.

Objectives: To describe initial and subsequent UDT results among patients diagnosed with cancer receiving outpatient palliative care (PC) at a tertiary cancer center.

Methods: A single center retrospective study including adult (≥18 years old) patients who established with an outpatient PC clinic at The Ohio State University (OSU) James Cancer Hospital from July 1, 2017 to June 30, 2019. Outcomes examined were two types of unexplained UDT results: 1) time to first presence of non-prescribed substance; and 2) time to first absence of prescribed substance. Both outcomes were plotted as a reverse Kaplan-Meier survival curve. Substances implicated in unexplained UDT results were summarized.

Results: A total of 1,141 patients and 2,459 UDTs were included. Mean patient age was 57 years, and the sample was 51% female and 83% White. Mean UDT per patient was 2.4 (SD=2.1). 15.1% of patients had an unexplained UDT. Among patients with an unexplained UDT, 45% were detected at baseline UDT. At 24 months, probability of: non-prescribed substance was 19.7% (95% CI (15.4, 24.9)); absence of prescribed substance was 18.6% (95% CI (14.1%, 24.4%)). Cocaine was the most common (18.1%) non-prescribed substance, and oxycodone (52.7%) was the most common absent substance.

Conclusion: Unexplained UDT results were captured at varying timepoints throughout PC engagement, supporting the use of baseline and subsequent UDTs to optimize patient safety in cancer symptom management. PC providers should consider continuing to use UDTs as a way to monitor medication adherence throughout PC engagement.